Selective dielectric resin application on circuitized core layers

ABSTRACT

A process of manufacturing a multiple-layer printed circuit board includes selectively applying a dielectric resin to a region of a circuitized core layer. The process also includes partially curing the dielectric resin prior to performing a lamination cycle to form the multiple-layer printed circuit board that includes the circuitized core layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of and claims priority fromU.S. patent application Ser. No. 15/845,781, filed Dec. 18, 2017, nowU.S. Pat. No. 10,405,421 granted Sep. 3, 2019.

BACKGROUND

A printed circuit board (PCB) laminate design may include amultiple-layer “stack-up” design that includes multiple layers. Forexample, a PCB may be formed of a fiberglass cloth pre-impregnated witha thermoset resin, also referred to as a “prepreg” material. Due to thecomplex nature of fluid flow properties for thermoset resins, design ofPCB lamination processes that use thermoset resins can be challenging.The complex nature of some multiple-layer PCB designs may make itparticularly difficult to accurately achieve a specific dielectricthickness and total board thickness while also maintaining asatisfactory impedance value. For example, high density interconnect(HDI) boards may incorporate microvias, blind and buried vias, multiplecontrolled impedance and differential traces, fine line technology, andtighter tolerances.

SUMMARY

According to an embodiment, a process of manufacturing a multiple-layerprinted circuit board is disclosed. The process includes selectivelyapplying a dielectric resin to a region of a circuitized core layer. Theprocess also includes partially curing the dielectric resin prior toperforming a lamination cycle to form a multiple-layer printed circuitboard that includes the circuitized core layer.

According to another embodiment, a multiple-layer printed circuit boardis disclosed. The multiple-layer printed circuit board is formedaccording to a process that includes selectively applying a dielectricresin to a region of a circuitized core layer and partially curing thedielectric resin. The process also includes forming a layup thatincludes a layer of pre-impregnated (prepreg) material adjacent to thepartially cured dielectric resin of the circuitized core layer. Theprocess further includes performing a lamination cycle to form amultiple-layer printed circuit board.

According to yet another embodiment, a circuitized core layer formultiple-layer printed circuit board manufacturing is disclosed. Thecircuitized core layer includes a partially cured dielectric resindisposed within a region associated with increased resin demand.

According to another embodiment, a process of manufacturing amultiple-layer printed circuit board is disclosed. The process includesselectively applying a dielectric resin mixture to a region of acircuitized core layer. The dielectric resin mixture includes glassspheres encapsulated within a dielectric resin. The process alsoincludes partially curing the dielectric resin prior to performing alamination cycle to form a multiple-layer printed circuit board thatincludes the circuitized core layer.

According to a further embodiment, a multiple-layer printed circuitboard is disclosed. The multiple-layer printed circuit board includes adielectric layer and a circuitized core layer. The dielectric layer isformed from a pre-impregnated (prepreg) material that includes apartially cured dielectric resin encapsulating a woven glass cloth. Thecircuitized core layer has a surface that is adjacent to the dielectriclayer. The surface of the circuitized core layer has a region ofdielectric material that includes glass spheres encapsulated within acured dielectric resin.

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a process of manufacturing amultiple-layer printed circuit board in which dielectric resin isselectively applied to region(s) of a circuitized core layer associatedwith increased resin demand, according to one embodiment.

FIG. 2 is a diagram illustrating a portion of a multiple-layer printedcircuit board that includes regions of increased resin demand, accordingto one embodiment.

FIG. 3A is a diagram illustrating regions of increased resin demandassociated with multiple circuitized core layers to be utilized to forma multiple-layer printed circuit board, according to one embodiment.

FIG. 3B is a diagram illustrating selective application of a dielectricresin to the regions of the circuitized core layers depicted in FIG. 3Aand partial curing of the dielectric resin, according to one embodiment.

FIG. 3C is a diagram illustrating a layup that includes the circuitizedcore layers with the partially cured dielectric resin of FIG. 3B priorto a lamination cycle, according to one embodiment.

FIG. 3D is a diagram illustrating that lamination of the layup of FIG.3C to form a multiple-layer printed circuit board results in curing ofthe dielectric resin within the regions of increased resin demand,according to one embodiment.

FIGS. 4A-4C are diagrams illustrating stages of a process of forming thefirst circuitized core layer depicted in FIGS. 3B and 3C by selectivelyapplying a dielectric resin to region(s) of increased resin demandfollowed by partial curing of the dielectric resin prior to performing alamination cycle, according to one embodiment.

FIGS. 5A-5C are diagrams illustrating stages of a process of forming thesecond circuitized core layer depicted in FIGS. 3B and 3C by selectivelyapplying a dielectric resin to region(s) of increased resin demandfollowed by partial curing of the dielectric resin prior to performing alamination cycle, according to one embodiment.

FIGS. 6A-6C are diagrams illustrating stages of a process of forming thethird circuitized core layer depicted in FIGS. 3B and 3C by selectivelyapplying a dielectric resin to region(s) of increased resin demandfollowed by partial curing of the dielectric resin prior to performing alamination cycle, according to one embodiment.

FIG. 7 is a flow diagram illustrating a particular embodiment of aprocess of manufacturing a multiple-layer printed circuit board thatincludes selectively applying and partially curing a dielectric resin inincreased resin demand region(s) of circuitized core layer(s) prior to alamination cycle.

DETAILED DESCRIPTION

The present disclosure describes selective application of dielectricresin to regions of increased resin demand of circuitized core layersprior to performing a lamination cycle to form a multiple-layer printedcircuit board. A dielectric resin may be applied to the regions ofincreased resin demand using inkjet printing techniques. Subsequently,the resin may be partially cured to form circuitized core layers havingpartially cured dielectric resin disposed within the regions ofincreased resin demand. During the lamination cycle, the partially cureddielectric resin fills the regions of increased resin demand with curedresin, thereby preventing resin starvation. In some embodiments of thepresent disclosure, a dielectric resin mixture that includes glassspheres encapsulated within a dielectric resin may be selectivelyapplied to the regions of increased resin demand. One potentialadvantage associated with the use of glass spheres is the ability tomore accurately match an overall dielectric constant of adjacentdielectric layers.

FIG. 1 is a diagram 100 illustrating a process of manufacturing amultiple-layer printed circuit board in which dielectric resin isselectively applied to region(s) of a circuitized core layer associatedwith increased resin demand, according to one embodiment. In the exampleof FIG. 1, selective application of resin to regions of a singlecircuitized core layer is illustrated. As illustrated and furtherdescribed herein with respect to FIGS. 2, 3A-3D, 4A-4C, 5A-5C, and6A-6C, multiple circuitized core layers of a particular multiple-layerprinted circuit board design may have dielectric resin selectivelyapplied in identified region(s) prior to performing a lamination cycle.

The left side of FIG. 1 depicts a process of forming a circuitized corelayer that includes regions of high resin demand. The first stagecorresponds to core lamination in which two epoxy glass layers (e.g.,two layers of prepreg material) are disposed between two outer layers ofcopper foil and laminated to form a raw core. In the example of FIG. 1,the outer layers of copper on the raw core correspond to voltage andground planes in a multiple-layer printed circuit board. The next stagedepicted on the left side of FIG. 1 corresponds to patterning of thecopper layer of the raw core to form a circuitized core. The circuitizedcore depicted in FIG. 1 identifies regions of increased resin demand fora multiple-layer printed circuit board formed from the circuitized core.

The right side of FIG. 1 depicts an example according to the presentdisclosure in which dielectric resin is selectively applied to theregions of increased resin demand and partially cured prior toperforming a lamination cycle to form a multiple-layer printed circuitboard that includes the circuitized core. The first stage depicted onthe right side of FIG. 1 illustrates that dielectric resin (“A-stage”resin) may be selectively applied to the identified regions of thecircuitized core and partially cured (“B-staged”) to form a circuitizedcore with resin. As described further herein, in some cases, the A-stageresin may correspond to a dielectric resin mixture that includes glassspheres encapsulated within a dielectric resin. The next stage depictedin FIG. 1 illustrates a selected portion of a layup that includes thecircuitized core with resin and a layer of pre-impregnated (prepreg)material adjacent to the B-staged resin to form a circuitized core plusprepreg. The next stage depicted in FIG. 1 illustrates that a laminationcycle results in a multiple-layer printed circuit board in which theselectively applied resin prevents resin starvation in the regions ofincreased resin demand.

Thus, FIG. 1 illustrates an example of a process of selectively applyingdielectric resin to high resin demand regions of a circuitized corelayer prior to a lamination cycle in order to prevent resin starvation.As described further herein, the dielectric resin may be selectivelyapplied using an inkjet printing process followed by partial curing(“B-staging”) of the resin. In some cases, the regions of increasedresin demand may be identified by fabricating a multiple-layer printedcircuit board from circuitized core layers without the dielectric resinfollowed by visual inspection to identify resin starved regions. Inother cases, an inverse of the copper pattern may be utilized toidentify the regions for resin dispensation via an inkjet printingprocess. For example, when a distance between adjacent copper tracessatisfies a threshold distance associated with increased resin demand,the region between the adjacent copper traces may be identified forresin dispensation.

FIG. 2 is a diagram 200 illustrating a portion of a multiple-layerprinted circuit board that includes regions of increased resin demand,according to one embodiment. In the example depicted in FIG. 2, themultiple-layer printed circuit board may be fabricated from a layup thatincludes three circuitized core layers with two intervening prepreglayers. Examples of circuitized core layers that may be utilized to formthe multiple-layer printed circuit board of FIG. 2 are illustrated andfurther described herein with respect to FIGS. 3A-3D. FIG. 2 furtherillustrates examples of regions of increased resin demand in each of thecircuitized core layers.

FIGS. 3A to 3D illustrate an example of a process of preventing resinstarvation in a multiple-layer printed circuit board by selectivelyapplying resin in region(s) of individual circuitized core layers thatare identified as increased resin demand region(s). In the exampledepicted in FIGS. 3A to 3D, three circuitized core layers are utilizedto form a multiple-layer printed circuit board. It will be appreciatedthat the processes described herein may be utilized for multiple-layerprinted circuit boards including an alternative number and/orarrangement of circuitized core layers.

Referring to FIG. 3A, a diagram 300 illustrates regions of increasedresin demand associated with multiple circuitized core layers to beutilized to form a multiple-layer printed circuit board, according toone embodiment.

In the example of FIG. 3A, the multiple circuitized core layers includea first circuitized core 302, a second circuitized core 304, and a thirdcircuitized core 306. FIG. 3A illustrates that the first circuitizedcore 302 includes a region 310 of increased resin demand, the secondcircuitized core 304 includes a region 312 of increased resin demand,and the third circuitized core 306 includes a region 314 of increasedresin demand. In some cases, the regions 310-314 of increased resindemand may be identified by fabricating a multiple-layer printed circuitboard from a layup that includes the three circuitized core layers302-306 without the dielectric resin followed by visual inspection toidentify resin starved regions. In other cases, an inverse of the copperpattern for each of the circuitized core layers 302-306 may be utilizedto identify the regions for resin dispensation via an inkjet printingprocess.

Referring to FIG. 3B, a diagram 320 illustrates selective application ofa dielectric resin to the regions of the circuitized core layersdepicted in FIG. 3A and partial curing of the dielectric resin,according to one embodiment. FIG. 3B illustrates that, followingselective application and partial curing, the first circuitized core 302includes B-stage resin 322 in the region 310, the second circuitizedcore 304 includes B-stage resin 322 in the region 312, and the thirdcircuitized core 306 includes B-stage resin 322 in the region 314. Insome cases, the B-stage resin 322 may correspond to a dielectric resinmixture that includes glass spheres encapsulated within a partiallycured dielectric resin.

The process of selectively applying dielectric resin onto the firstcircuitized core 302 and partially curing the dielectric resin to formthe B-stage resin 322 is illustrated and further described herein withrespect to FIGS. 4A-4C. The process of selectively applying dielectricresin onto the second circuitized core 304 and partially curing thedielectric resin to form the B-stage resin 322 is illustrated andfurther described herein with respect to FIGS. 5A-5C. The process ofselectively applying dielectric resin onto the third circuitized core306 and partially curing the dielectric resin to form the B-stage resin322 is illustrated and further described herein with respect to FIGS.6A-6C.

Referring FIG. 3C, a diagram 330 illustrates a layup 332 that includesthe circuitized core layers 302-306 with the partially cured dielectricresin of FIG. 3B prior to a lamination cycle, according to oneembodiment.

FIG. 3C illustrates that the layup 332 includes a first prepreg layer334 disposed between a bottom surface of the first circuitized corelayer 302 that includes the B-stage resin 322 and a top surface of thesecond circuitized core layer 304 (that does not include the B-stageresin 322). The layup 332 further includes a second prepreg layer 336disposed between a bottom surface of the second circuitized core layer304 (that includes the B-stage resin 322) and a top surface of the thirdcircuitized core layer 306 (that includes the B-stage resin 322).

Referring FIG. 3D, a diagram 340 illustrates that lamination of thelayup 332 of FIG. 3C to form a multiple-layer printed circuit boardresults in curing of the B-stage resin 322, according to one embodiment.The lamination cycle depicted in FIG. 3D includes disposing the layup332 between a top platen 342 and a bottom platen 344, and applyingpressure and heat. The lamination cycle results in curing of the B-stageresin 322 to form cured resin 346 in each of the regions 310-314 ofincreased resin demand, thereby preventing resin starvation in themultiple-layer printed circuit board. In some cases, the cured resin 346may correspond to a dielectric resin mixture that includes glass spheresencapsulated within a cured dielectric resin.

FIGS. 4A-4C are diagrams illustrating stages of a process of forming thefirst circuitized core layer depicted in FIGS. 3B and 3C by selectivelyapplying a dielectric resin to region(s) of increased resin demandfollowed by partial curing of the dielectric resin prior to performing alamination cycle, according to one embodiment.

Referring to FIG. 4A, a diagram 400 illustrates a cross-sectional viewand a top view of the surface of the first circuitized core 302 of FIG.3A. FIG. 4A illustrates that the region 310 of increased resin demandmay correspond to a relatively narrow gap between two copper traces onthe first circuitized core 302. The top view illustrates that the region310 may be identified by coordinates along an X-axis and a Y-axis. Asillustrated and further described herein with respect to FIG. 4B, thecoordinates along the X-axis and the Y-axis may be utilized by an inkjetprinter for resin dispensation.

Referring to FIG. 4B, a diagram 410 illustrates a cross-sectional viewand a top view of the surface of the first circuitized core 302 of FIG.4A after resin dispensation into the region 310 of increased resindemand. In the embodiment depicted in FIG. 4B, the coordinates of theregion 310 along the X-axis and the Y-axis may be utilized to dispense apattern of individual “droplets” of resin 412 (identified as “Inkjetprinted resin” in FIG. 4B) in a manner similar to dispensation of ink byan inkjet printer. The resin 412 dispensed within the region 310represents an “A-stage” resin. In some cases, the resin 412 depicted inFIG. 4B may correspond to a dielectric resin mixture that includes glassspheres (e.g., hollow glass spheres) encapsulated within a dielectricresin. For example, the glass spheres may correspond to hollow glassspheres formed from a glass material (e.g., an “E-glass” material) thatis substantially similar to a woven glass cloth of the adjacent prepreglayer 334 in the layup 332 (depicted in in FIG. 3C). Referring to themultiple-layer printed circuit board depicted in FIG. 3D, the curedresin 346 within the region 310 of the first circuitized core 302 mayhave an overall dielectric constant that is substantially similar to anoverall dielectric constant of the adjacent dielectric layer formed fromthe first prepreg layer 334.

FIG. 4C is a diagram 420 illustrating that the “A-stage” resin 412dispensed within the region 310, as shown in FIG. 4B, is then partiallycured (“B-staged”) to form the B-stage resin 322. In some cases, theB-stage resin 322 depicted in FIG. 4C may correspond to a dielectricresin mixture that includes glass spheres (e.g., hollow glass spheres)encapsulated within a partially cured dielectric resin.

In some cases, the resin 412 dispensed within the region 310 may beselected based on the resin associated within an adjacent prepreg layerduring a subsequent lamination cycle to form a multiple-layer printedcircuit board. For example, referring to the layup 332 depicted in FIG.3C, the resin 412 dispensed within the region 310 may be selected basedon the resin associated with the first prepreg layer 334 adjacent to thefirst circuitized core layer 302. To illustrate, the “A-stage” resin 412may be selected such that, after “B-staging”, the B-stage resin 322corresponds to the B-staged resin within the first prepreg layer 334.

In other cases, the resin 412 dispensed within the region 310 may beselected such that, after the lamination cycle depicted in FIG. 3D, thecured resin 346 has a dielectric constant that is substantially similarto a dielectric constant of the adjacent dielectric layer formed fromthe first prepreg layer 334. That is, the resin 412 selected fordispensation within the region 310 may be different from the resinassociated with the first prepreg layer 334 in order to match an overalldielectric constant of the woven glass cloth and cured resin after thelamination cycle.

FIGS. 5A-5C are diagrams illustrating stages of a process of forming thesecond circuitized core layer depicted in FIGS. 3B and 3C by selectivelyapplying a dielectric resin to region(s) of increased resin demandfollowed by partial curing of the dielectric resin prior to performing alamination cycle, according to one embodiment.

Referring to FIG. 5A, a diagram 500 illustrates a cross-sectional viewand a top view of the surface of the second circuitized core 304 of FIG.3A. FIG. 5A illustrates that the region 312 of increased resin demandmay correspond to a relatively narrow area between a plated through hole(PTH) and copper of the ground plane (as depicted in FIG. 2). The topview illustrates that the region 312 may be identified by coordinatesalong an X-axis and a Y-axis. As illustrated and further describedherein with respect to FIG. 5B, the coordinates along the X-axis and theY-axis may be utilized by an inkjet printer for resin dispensation.

Referring to FIG. 5B, a diagram 510 illustrates a cross-sectional viewand a top view of the surface of the second circuitized core 304 of FIG.5A after resin dispensation into the region 312 of increased resindemand. In the embodiment depicted in FIG. 5B, the coordinates of theregion 312 along the X-axis and the Y-axis may be utilized to dispense apattern of individual “droplets” of resin 512 (identified as “Inkjetprinted resin” in FIG. 5B) in a manner similar to dispensation of ink byan inkjet printer. The resin 512 dispensed within the region 312represents an “A-stage” resin. In some cases, the resin 512 depicted inFIG. 5B may correspond to a dielectric resin mixture that includes glassspheres (e.g., hollow glass spheres) encapsulated within a dielectricresin. For example, the glass spheres may correspond to hollow glassspheres formed from a glass material (e.g., an “E-glass” material) thatis substantially similar to a woven glass cloth of the adjacent prepreglayer 336 in the layup 332 (depicted in in FIG. 3C). Referring to themultiple-layer printed circuit board depicted in FIG. 3D, the curedresin 346 within the region 312 of the second circuitized core 304 mayhave an overall dielectric constant that is substantially similar to anoverall dielectric constant of the adjacent dielectric layer formed fromthe second prepreg layer 336.

FIG. 5C is a diagram 520 illustrating that the “A-stage” resin 512dispensed within the region 312, as shown in FIG. 5B, is then partiallycured (“B-staged”) to form the B-stage resin 322. In some cases, theB-stage resin 322 depicted in FIG. 5C may correspond to a dielectricresin mixture that includes glass spheres (e.g., hollow glass spheres)encapsulated within a partially cured dielectric resin.

In some cases, the resin 512 dispensed within the region 312 may beselected based on the resin associated within an adjacent prepreg layerduring a subsequent lamination cycle to form a multiple-layer printedcircuit board. For example, referring to the layup 332 depicted in FIG.3C, the resin 512 dispensed within the region 312 may be selected basedon the resin associated with the second prepreg layer 336 adjacent tothe second circuitized core 304. To illustrate, the “A-stage” resin 512may be selected such that, after “B-staging”, the B-stage resin 322corresponds to the B-staged resin within the second prepreg layer 336.

In other cases, the resin 512 dispensed within the region 312 may beselected such that, after the lamination cycle depicted in FIG. 3D, thecured resin 346 has a dielectric constant that is substantially similarto a dielectric constant of the adjacent dielectric layer formed fromthe second prepreg layer 336. That is, the resin 512 selected fordispensation within the region 312 may be different from the resinassociated with the second prepreg layer 336 in order to match anoverall dielectric constant of the woven glass cloth and cured resinafter the lamination cycle.

FIGS. 6A-6C are diagrams illustrating stages of a process of forming thethird circuitized core layer depicted in FIGS. 3B and 3C by selectivelyapplying a dielectric resin to region(s) of increased resin demandfollowed by partial curing of the dielectric resin prior to performing alamination cycle, according to one embodiment.

Referring to FIG. 6A, a diagram 600 illustrates a cross-sectional viewand a top view of the surface of the third circuitized core 306 of FIG.3A. FIG. 6A illustrates that the region 314 of increased resin demandmay correspond to a relatively narrow gap between two copper traces onthe third circuitized core 306. The top view illustrates that the region314 may be identified by coordinates along an X-axis and a Y-axis. Asillustrated and further described herein with respect to FIG. 6B, thecoordinates along the X-axis and the Y-axis may be utilized by an inkjetprinter for resin dispensation.

Referring to FIG. 6B, a diagram 610 illustrates a cross-sectional viewand a top view of the surface of the third circuitized core 306 of FIG.6A after resin dispensation into the region 314 of increased resindemand. In the embodiment depicted in FIG. 6B, the coordinates of theregion 314 along the X-axis and the Y-axis may be utilized to dispense apattern of individual “droplets” of resin 612 (identified as “Inkjetprinted resin” in FIG. 6B) in a manner similar to dispensation of ink byan inkjet printer. The resin 612 dispensed within the region 314represents an “A-stage” resin. In some cases, the resin 612 depicted inFIG. 6B may correspond to a dielectric resin mixture that includes glassspheres (e.g., hollow glass spheres) encapsulated within a dielectricresin. For example, the glass spheres may correspond to hollow glassspheres formed from a glass material (e.g., an “E-glass” material) thatis substantially similar to a woven glass cloth of the adjacent prepreglayer 336 in the layup 332 (depicted in in FIG. 3C). Referring to themultiple-layer printed circuit board depicted in FIG. 3D, the curedresin 346 within the region 314 of the third circuitized core 306 mayhave an overall dielectric constant that is substantially similar to anoverall dielectric constant of the adjacent dielectric layer formed fromthe second prepreg layer 336.

FIG. 6C is a diagram 620 illustrating that the “A-stage” resin 612dispensed within the region 314, as shown in FIG. 6B, is then partiallycured (“B-staged”) to form the B-stage resin 322. In some cases, theB-stage resin 322 depicted in FIG. 6C may correspond to a dielectricresin mixture that includes glass spheres (e.g., hollow glass spheres)encapsulated within a partially cured dielectric resin.

In some cases, the resin 612 dispensed within the region 314 may beselected based on the resin associated within an adjacent prepreg layerduring a subsequent lamination cycle to form a multiple-layer printedcircuit board. For example, referring to the layup 332 depicted in FIG.3C, the resin 612 dispensed within the region 314 may be selected basedon the resin associated with the second prepreg layer 336 adjacent tothe third circuitized core 306. To illustrate, the “A-stage” resin 612may be selected such that, after “B-staging”, the B-stage resin 322corresponds to the B-staged resin within the second prepreg layer 336.

In other cases, the resin 612 dispensed within the region 314 may beselected such that, after the lamination cycle depicted in FIG. 3D, thecured resin 346 has a dielectric constant that is substantially similarto a dielectric constant of the adjacent dielectric layer formed fromthe second prepreg layer 336. That is, the resin 612 selected fordispensation within the region 314 may be different from the resinassociated with the second prepreg layer 336 in order to match anoverall dielectric constant of the woven glass cloth and cured resinafter the lamination cycle.

FIG. 7 is a flow diagram illustrating a particular embodiment of aprocess 700 of manufacturing a multiple-layer printed circuit board thatincludes selectively applying and partially curing a dielectric resin inincreased resin demand region(s) of circuitized core layer(s) prior to alamination cycle. In some cases, the dielectric resin may correspond toa dielectric resin mixture that includes glass spheres encapsulatedwithin a dielectric resin. In a particular embodiment, the glass spheresmay correspond to hollow glass spheres formed from a glass material(e.g., an “E-glass” material) that is substantially similar to a wovenglass cloth material of a pre-impregnated material to be utilized toform dielectric layers in a multiple-layer printed circuit board. Thismay enable the region of the circuitized core layer including the glassspheres and cured dielectric resin to have a dielectric constant that issubstantially similar to a dielectric constant associated with anadjacent dielectric layer formed from the prepreg material.

In some embodiments, the process 700 depicted in FIG. 7 may be utilizedto form a multiple-layer printed circuit board that includes adielectric layer and a circuitized core layer. The dielectric layer isformed from a prepreg material that includes a partially cureddielectric resin encapsulating a woven glass cloth. The circuitized corelayer has a surface that is adjacent to the dielectric layer. Thesurface of the circuitized core layer has a region of dielectricmaterial that includes glass spheres encapsulated within a cureddielectric resin.

The process 700 includes identifying one or more regions of acircuitized core layer associated with increased dielectric resindemand, at 702. For example, referring to FIGS. 3A and 4A, the region310 of the first circuitized core 302 is associated with increaseddielectric resin demand. As another example, referring to FIGS. 3A and5A, the region 312 of the second circuitized core 304 is associated withincreased dielectric resin demand. As a further example, referring toFIGS. 3A and 6A, the region 314 of the third circuitized core 306 isassociated with increased dielectric resin demand.

The process 700 includes selectively applying a dielectric resin to theregion(s) of the circuitized core layer, at 704. For example, referringto FIG. 4B, the resin 412 may be inkjet printed into the region 310 ofthe first circuitized core 302 (e.g., based on X-Y coordinates of theregion 310, as depicted in the top view). As another example, referringto FIG. 5B, the resin 512 may be inkjet printed into the region 312 ofthe second circuitized core 304 (e.g., based on X-Y coordinates of theregion 312, as depicted in the top view). As a further example,referring to FIG. 6B, the resin 612 may be inkjet printed into theregion 314 of the third circuitized core 306 (e.g., based on X-Ycoordinates of the region 314, as depicted in the top view). In somecases, the dielectric resin may correspond to a dielectric resin mixturethat includes glass spheres encapsulated within a dielectric resin.

The process 700 includes partially curing the dielectric resin, at 706.For example, referring to FIG. 4C, partially curing the resin 412dispensed within the region 310 forms the B-stage resin 322 within theregion 310 of the first circuitized core 302. As another example,referring to FIG. 5C, partially curing the resin 512 dispensed withinthe region 312 forms the B-stage resin 322 within the region 312 of thesecond circuitized core 304. As a further example, referring to FIG. 6C,partially curing the resin 612 dispensed within the region 314 forms theB-stage resin 322 within the region 314 of the third circuitized core306. In some embodiments, the B-stage resin 322 depicted in FIGS. 4C,5C, and 6C may correspond to a dielectric resin mixture that includesglass spheres encapsulated within a partially cured dielectric resin.

The process 700 includes forming a layup that includes the circuitizedcore layer, at 708. For example, referring to FIG. 3C, the layup 332includes the first circuitized core 302 with the B-stage resin 322within the region 310 of increased resin demand. The region 310 of thefirst circuitized core 302 is adjacent to the first prepreg layer 334 inthe layup 332. As another example, referring to FIG. 3C, the layup 332includes the second circuitized core 304 with the B-stage resin 322within the region 312 of increased resin demand. The region 312 of thesecond circuitized core 304 is adjacent to the second prepreg layer 336in the layup 332. As a further example, referring to FIG. 3C, the layup332 includes the third circuitized core 306 with the B-stage resin 322within the region 314 of increased resin demand. The region 314 of thethird circuitized core 306 is adjacent to the second prepreg layer 336in the layup 332.

The process 700 includes performing a lamination cycle to form amultiple-layer printed circuit board, at 710. For example, referring toFIG. 3D, the layup 332 of FIG. 3C may be disposed between the top platen342 and the bottom platen 344, and the lamination cycle may includeapplying pressure and heat. The resulting multiple-layer printed circuitboard includes the cured resin 346 in the regions 310-314 of increasedresin demand, thereby preventing resin starvation. In some cases, thecured resin 346 may correspond to a dielectric resin mixture thatincludes glass spheres encapsulated within a cured dielectric resin.This may enable the region of the circuitized core layer that includesthe cured resin 346 to have a first dielectric constant that issubstantially similar to a second dielectric constant associated with anadjacent dielectric layer formed from the prepreg material.

Thus, FIG. 7 illustrates an example of a process of manufacturing amultiple-layer printed circuit board that includes selectively applyingand partially curing a dielectric resin in increased resin demandregion(s) of circuitized core layer(s) prior to a lamination cycle. Theadditional dielectric resin may fill the regions of increased resindemand during the lamination cycle, thereby preventing resin starvation.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

What is claimed is:
 1. A process of manufacturing a multiple-layerprinted circuit board, the process comprising: identifying a region of acircuitized core layer, the region of the circuitized core layerassociated with increased dielectric resin demand; selectively applyinga dielectric resin to the identified region of the circuitized corelayer; and partially curing the dielectric resin prior to performing alamination cycle and forming the multiple-layer printed circuit boardthat includes the circuitized core layer.
 2. The process of claim 1,wherein selectively applying the dielectric resin includes utilizing aninkjet printer to dispense the dielectric resin within the region. 3.The process of claim 1, further comprising: forming a layup thatincludes a layer of pre-impregnated material adjacent to the region ofthe circuitized core layer; and performing the lamination cycle to formthe multiple-layer printed circuit board from the layup.
 4. The processof claim 3, wherein the partially cured dielectric resin issubstantially similar to a partially cured resin within the layer ofpre-impregnated material.
 5. The process of claim 1, further comprising:selectively applying the dielectric resin to a second region of thecircuitized core layer; and partially curing the dielectric resin priorto performing the lamination cycle.
 6. The process of claim 5, whereinthe dielectric resin is selectively applied to a surface of thecircuitized core layer adjacent to a location of a plated through hole(PTH) to be formed after the lamination cycle.
 7. The process of claim1, wherein the dielectric resin is applied between adjacent coppertraces of the circuitized core layer.
 8. The process of claim 7, whereina distance between the adjacent copper traces satisfies a thresholddistance associated with increased dielectric resin demand.
 9. Theprocess of claim 1 wherein the dielectric resin mixture is selectivelyapplied between adjacent copper traces of the circuitized core layerthat are separated by a threshold distance associated with increasedresin demand.
 10. A process of manufacturing a multiple-layer printedcircuit board, the process comprising: identifying a region of acircuitized core layer, the region of the circuitized core layerassociated with increased dielectric resin demand; selectively applyinga dielectric resin to the identified region of the circuitized corelayer; selectively applying the dielectric resin to a second region ofthe circuitized core layer; partially curing the dielectric resin priorto performing a lamination cycle and forming the multiple-layer printedcircuit board that includes the circuitized core layer wherein thepartially cured dielectric resin is substantially similar to a partiallycured resin within the layer of pre-impregnated material; forming alayup that includes a layer of pre-impregnated material adjacent to theregion of the circuitized core layer; and performing the laminationcycle to form the multiple-layer printed circuit board from the layup.11. The process of claim 10 wherein the dielectric resin is selectivelyapplied to a surface of the circuitized core layer adjacent to alocation of a plated through hole (PTH) to be formed after thelamination cycle.
 12. The process of claim 10 wherein the dielectricresin is applied between adjacent copper traces of the circuitized corelayer.
 13. The process of claim 12 wherein a distance between theadjacent copper traces satisfies a threshold distance associated withincreased resin demand.
 14. The process of claim 10 wherein selectivelyapplying the dielectric resin includes utilizing an inkjet printer todispense the dielectric resin within the region.